Pathological gambling (PG) has become a major public health concern due to an unprecedented rate of growth of legalized gambling venues such as casinos and state lotteries over the past two decades; the prevalence of PG in the United States is predicted to increase with the increased access to gambling opportunities. However, the currently low lifetime prevalence of PG disorder of about 1-2% in the United States, coupled with low rates of treatment seeking among those affected, poses a considerable challenge for current epidemiologic research. This application successfully deals with this problem, by identifying a setting, Australia, where the prevalence of PG is now higher than it currently is in the United States. Australia is the ideal setting in which to conduct a community-based study of PG, and is also well suited for a genetic epidemiologic investigation because it will allow for an examination of the genetic influence on PG susceptibility in a culture in which most individuals have been heavily exposed to gambling opportunities. The broad aim of this proposal is to examine, using epidemiologic and biometrical modeling approaches, the causes of PG and problem gambling among both women and men. Telephone interview assessments of PG and problem gambling and questionnaire assessments of personality and antisocial behavior disorders will be conducted with a target sample of 10,518 individuals (5,885 women, 4,633 men) from 5,259 twin pairs (2,235 monozygotic pairs, 1,697 same-sex dizygotic pairs, and 1,327 unlike-sex dizygotic pairs) from the national Australian Twin Registry. These data will be analyzed in conjunction with structured psychiatric interview assessments of lifetime history of alcohol dependence, major depression, and conduct disorder collected in 1992-1994 or 1996-2000 and questionnaire assessments of major dimensions of personality collected in 1988 or 1989 in order to examine: (a) the relative contributions of genetic and environmental factors to the risk for PG and problem gambling, (b) the lifetime co-occurrence of PG and problem gambling with alcohol dependence and comorbid psychiatric disorders and the causes of co-occurrence, and (c) the role of personality in the etiology and comorbidity of PG and problem gambling. [unreadable] [unreadable]